Surface coatings

ABSTRACT

The invention provides a method of coating a fabric, e.g. a textile material, with a polymer coating, which method comprises contacting a fabric with a monomer and subjecting the monomer to low power plasma polymerization, wherein the monomer comprises the general formula (I): C n F 2n+1 C m X 2m CR 1 Y—OCO—C(R 2 )═CH 2 , wherein n is 2 to 6, m is 0 to 9, X and Y are H, F, Cl, Br or I, R 1  is H or alkyl, e.g. —CH 3 , or a substituted alkyl, e.g. an at least partially halo-substituted alkyl, and R 2  is H or alkyl, e.g. —CH 3  or a substituted alkyl, e.g. an at least partially halo-substituted alkyl.

This application claims the benefit of GB Application No. 1218055.0filed Oct. 9, 2012, GB Application No. 1316115.3 filed Sep. 10, 2013,and PCT/EP2013/071018 filed Oct. 9, 2013, International Publication No.WO 2014/056966 A1, and the amended sheets from the IPRP, which arehereby incorporated by reference in their entirety as if fully set forthherein.

The present invention relates to methods for applying surface coatingsand is especially, but not exclusively, related to methods fordepositing protective polymer coatings onto fabrics and the resultantcoated fabrics.

The words fabric or fabrics as used in this application includesmaterials that are not woven as well as woven or knitted textiles, whichmay be manufactured into articles such as items of apparel forapplication in daily use, in industrial environments, in personalprotective equipment (PPE), in sport and leisure environments and so on.Other articles into which fabrics may be manufactured as well arecommodities, such as backpacks, umbrellas, tents, blinds, screens,canopies, tapestry, household textiles, sleeping bags etc. Fabrics arealso utilised as filtration media articles for use, for example, inheating, ventilation or air conditioning (HVAC) systems or for use inexhaust filters, diesel filters, liquid filters, filtration media formedical applications and so on. Frequently, in HVAC applications,fabrics are not woven, knitted or otherwise formed into materials with aregular fibre structure or regular arrangement of the fibres. Themethods and processes of this invention are applicable to all suchfabrics.

BACKGROUND OF THE INVENTION

It is known to coat fabrics with coatings, e.g. polymer coatings, forthe purpose of protecting the fabric from wear such as that experiencedduring everyday use or during repeated wash cycles.

Prior art methods of depositing the coatings describe polymerisingfluorocarbon gas precursors such as tetrafluoromethane (CF₄),hexafluoroethane (C₂F₆), hexafluoropropylene (C₃F₆) or octafluoropropane(C₃F₈) using plasma deposition techniques. Other precursor monomers suchas fluorohydrocarbons, e.g. CF₃H or C₂F₄H₂ or fluorocarbonethers such asCF₃OCF₃ or long chain acrylates or methacrylates having perfluorocarbonchain lengths of eight carbons or more, such as1H,1H,2H,2H—heptadecafluorodecyl acrylate (FC8), are also described inthe prior art.

However, these particular classes of precursor molecules require highpower plasma or pulsed plasma in order to initiate the polymerisationreaction. Moreover, such precursor molecules may also require highprecursor gas flow rates and long deposition times in order to obtain anacceptable thickness of the polymer layer.

A problem that may arise when using high precursor gas flow rates and/orhigh power or pulsed plasma is that the resultant polymer coatings mayhave a non-uniform thickness. For instance, high power plasma causesmonomers to fragment which can result in unpredictable deposition of thepolymer and hence substandard coatings.

Another problem that may arise when utilising fluorocarbon gas precursormolecules such as those described above is that the subsequently formedpolymer layer has limited hydrophobicity and oleophobicity. Typicalcontact angles for water that can be achieved with such coatings aremaximum 90 to 100°. The resistance to oil is also limited to maximumlevel 3 to 4 according to ISO14419.

Another problem is that acrylates and methacrylates havingperfluorocarbon chain lengths of eight carbons or more may containsignificant levels of the hazardous, carcinogenic, chemicalperfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS),which have been the recent subject of investigation into adverse healtheffects of humans.

SUMMARY OF THE INVENTION

Another aspect is that for many of the prior art monomer precursors,gaseous and liquid, a carrier gas, e.g. an inert gas such as argon orhelium, is used to generate the plasma. More, in prior art documents theratio carrier gas/monomer indicates the use of more carrier gas thanmonomer precursor gas, e.g. ratios of 100:1 to 2:1.

It is a first non-exclusive aspect of the invention to provide a methodfor depositing a protective coating to a fabric, the method utilisinglow plasma power and/or low monomer flow rates and/or benign plasmaconditions.

It is a second non-exclusive aspect to provide more resilient layers,layers with one or both of better in situ performance and increaseduniformity, e.g. so as to which increase the lifespan of a fabric.

It is a third non-exclusive aspect to provide a coating for fabrics withhigh levels of hydrophobicity and/or oleophobicity, for instance so thatitems of apparel or commodities that are formed subsequently from thefabric are sufficiently water and/or oil proof. Because certain types ofair filtration media are electrostatically charged it is desirable toprovide coatings having high levels of hydrophobicity and/oroleophobicity in order to reduce discharge of electrets in case ofcontact with a discharging material, e.g. isopropanol, without adverselyaffecting the properties, e.g. filtration properties, of the fabric.

It is a fourth non-exclusive aspect to provide a safer, non-toxicprotective coating for fabrics.

A first aspect of the present invention provides a method of coating afabric, including a textile material, with a polymer coating, whichmethod includes contacting a fabric with a monomer and subjecting themonomer to low power plasma polymerisation, wherein the monomercomprises the general formula (I):C_(n)F_(2n+1)C_(m)X_(2m)CR₁Y—OCO—C(R₂)═CH₂  (I)wherein n is 2 to 6, m is 0 to 9, X and Y are H, F, Cl, Br or I, R₁ is Hor alkyl or a substituted alkyl, e.g. an at least partiallyhalo-substituted alkyl, and R₂ is H or alkyl or a substituted alkyl,e.g. an at least partially halo-substituted alkyl.

Preferably, the method includes the step of coating the fabric as thefabric is passed by unwinding from a first roller on which the fabric isplaced into the apparatus for coating it and being wound onto a secondroller.

Preferably, the method includes the step of coating the fabric as thefabric is guided between a first roller and a second roller.

Preferably, the method includes the step of coating one or both surfacesof a sheet of fabric.

Before deposition of the coating, it might be advantageous to gas out(or out-gas) the textile and to apply an activation and/or cleaningstep. By gassing out the textile, which is normally stored on a rollprior to coating, the base pressures that are achievable in a coatingapparatus or plasma chamber are lower than without the gassing out (oroutgassing), which leads to a better coating quality. The gassing outtakes place during the pumping down by removing and pumping away allmoisture present in or on the surface of the textile material. The timeneeded for gassing out depends on the type of polymers used to make thetextile. Natural fibres, e.g. cotton, tend to have a higher rate ofretention of water in comparison to synthetic fibres.

Preferably, the gassing out of the roll of textile is done as thetextile is unwound, passed through the plasma zone and wound onto asecond roller in a first processing step. Before starting the outgassingstep, the plasma chamber containing the roll is pumped down to apre-determined low base pressure. Once this base pressure is reached,the outgassing starts by unwinding the textile from the roll withoutturning on the power source to avoid the presence of plasma in thechamber. As the pump is continuously pumping, moisture and trapped gasessuch as oxygen, nitrogen, carbon dioxide, noble gases and the like, areremoved from the textile and away from the plasma chamber as the fabricis unwound from one roller and passes through the plasma zone without aplasma being present to be wound onto a second roller.

Depending upon the nature of the fabric, more complete outgassing can beachieved by repeating the process of unrolling the fabric and rolling itback onto a second roller. This may be repeated several times,particularly in the cases of natural fibres such as cotton or wool whichtend to have a greater rate of absorption and retention of moisture thanthe synthetic fabrics.

When after the outgassing step the pressure inside the chamber is belowa set base pressure for pre-treatment or below a set base pressure forcoating, the next step, respectively the pre-treatment or the coating,can be started. If the set base pressure for pre-treatment or coatinghas not been reached, a second outgassing step can be executed byrewinding the textile from the second roller through the plasma zone tothe first roller, while the pumping is continued and no plasma isgenerated inside the plasma zone.

If required, a third, fourth, fifth, etc. outgassing step can be done inthe same way as described above by winding the textile back and forth.

The main advantage of this unrolling and re-rolling method of gassingout is the fact that moisture and trapped gases are removed fasterbecause when gassing out is done on a complete roll without unwindingbut only by pumping down without unwinding, the moisture and trappedgases held or found in the layers of textile close to the core of theroll tend to need long pumping times to be removed compared to the timesrequired if the textile is unrolled because, for example, in most casesthe moisture in those inner layers of fabric on a complete roll is notsufficiently removed, even for very long pumping times.

Preferably, during the outgassing, the fabric runs at a speed from 1 to30 m/min, for example 2 to 20 m/min, such as 3 m/min to 15 m/min, mostpreferably at approximately 5 to 10 m/min.

Preferably, the speed at which the second, third, fourth, etc.outgassing step takes place is equal to or higher than the speed of thefirst outgassing step. Whether the speed is increased or not dependsupon a variety of factors such as the composition of the fabric,(whether it includes natural fibres such as cotton of wool or is asynthetic fibre such as a polymer or polymers, the thickness, theconstruction, etc.).

Preferably the tension at which the fabric is wound is equal to thetension at which the coating takes place.

With this improved way of gassing out, a larger amount of moisture andtrapped gases is removed and it is also done in a reduced time, which isbeneficial for both coating quality and total processing time.

A pre-treatment in the form of an activation and/or cleaning and/oretching step might be advantageous towards the adhesion andcross-linking of the polymer coating.

Adhesion of the polymer coating to the fabric is essential for ensuringgood and durable coatings capable of withstanding repeated washing ofplasma coated textiles. In most cases, textiles contain residues as aresult of manufacture processes used to make the textile, e.g. dyeing,weaving, warping, even yarn spinning. When such a textile is coated witha polymer, a substantial part of the polymer coating binds with theseresidues, and during washing a portion of the residue(s) is removedtogether with the coating. A pre-treatment in the form of an activationand/or cleaning and/or etching step removes these residues and preparesthe textile for better binding of the polymer coating, therebyincreasing the durability of the coated textile, e.g. during washing.

Preferably, this pre-treatment is done using inert gases, such as argon,nitrogen or helium, but also more reactive gases might be used, e.g.hydrogen and oxygen and/or etching reagents such as CF₄. Thepre-treatment is performed with continuous wave plasma or pulsed waveplasma for short residence times in the plasma zone.

Preferably, the activation and/or cleaning and/or etching runs at aspeed from 1 to 30 m/min, for example 2 to 20 m/min, such as 3 m/min to15 m/min, most preferably at approximately 5 to 10 m/min.

Preferably the tension at which the fabric is wound is equal to thetension at which the coating takes place.

Preferably, when applied in continuous wave mode in a 9000 l chamber,the pre-treatment takes place at 25 to 10000 W, more preferably 50 to9000 W, even more preferably at 100 to 8000 W, and further preferably200 to 7500 W, and preferably still from 250 to 7000, 6750, 6500, 6250,6000, 5750, 5550, 5250, 5000, 4750, 4500, 4250, 4000, 3750, 3500, 3250,3000, 2900, 2800, 2750, 2700, 2600, 2500, 2400, 2300, 2250, 2200, 2100,2000, 1900, 1800, 1750, 1700, 1600, 1500, 1400, 1300, 1250, 1200, 1100,1000, 950, 900, 850, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350,or 300 W.

Preferably, when applied in pulsed wave mode in a 9000 l chamber, thepre-treatment takes place at a peak power value of 25 to 10000 W, morepreferably 50 to 9000 W, even more preferably at 100 to 8000 W, andfurther preferably at 200 to 7500 W, and preferably still at 250 to7000, 6750, 6500, 6250, 6000, 5750, 5550, 5250, 5000, 4750, 4500, 4250,4000, 3750, 3500, 3250, 3000, 2900, 2800, 2750, 2700, 2600, 2500, 2400,2300, 2250, 2200, 2100, 2000, 1900, 1800, 1750, 1700, 1600, 1500, 1400,1300, 1250, 1200, 1100, 1000, 950, 900, 850, 800, 750, 700, 650, 600,550, 500, 450, 400, 350, or 300 W.

It will be appreciated that the power and power mode at which thepre-treatment is performed depends on the gas or gas mixture used,and/or on the dimensions of the chamber and/or the design, size and/ornumber of electrodes present in the chamber.

In a first embodiment, the total coating process comprises one singlestep, i.e. a coating step, whereby no gassing out and no pre-treatmentis undertaken prior to coating the textile.

In another embodiment, the total coating process comprises three steps,each step including unwinding the textile, passing the textile through aplasma zone and winding up the textile, the steps including: a step forgassing out the textile; a pre-treatment step such as a plasma cleaningand/or activation and/or etching; and a coating step.

For the pre-treatment step, the winding up zone of the outgassingbecomes the unwinding zone of the pre-treatment and the unwinding zoneof the outgassing becomes the winding up zone of the pre-treatment. Forthe coating, the winding up zone of the pre-treatment becomes theunwinding zone of the coating and the unwinding zone of thepre-treatment becomes the winding up zone of the coating.

In a further embodiment, the total coating process comprises two steps,each step including unwinding the textile, passing it through the plasmazone and winding it up, the steps including: a step for combined gassingout and pre-treating (activating and/or cleaning and/or etching) thetextile; and a coating step. For the combined gassing out andpre-treatment both processes take place at the same time.

For the coating step, the winding up zone of the first step becomes theunwinding zone of the coating and the unwinding zone of the first stepbecomes the winding up zone of the coating.

Alternatively, the method may include the step of coating the fabricwith a polymer coating whilst the fabric, e.g. an article of apparel, isfixedly positioned inside the plasma chamber.

Preferably, R₁ is H, R₂ is H, and Y is H.

Preferably, m is 1 to 9.

Preferred examples of the monomer include acrylates and methacrylateshaving perfluorocarbon backbones comprising two to six carbon atoms,such as 1H,1H,2H,2H-Perfluorooctyl methacrylate or1H,1H,2H,2H-Perfluorooctyl acrylate.

Preferably, the method includes the step of utilising the monomer tostrike the plasma to form the deposited polymer coating. Advantageously,there is no need to utilise an additional gas to strike the plasma.

Preferably, the method includes the step of applying a polymer coatinghaving a thickness of from 10 to 500 nm, more preferably of from 10 to250 nm, even more preferably of from 20 to 150 nm, e.g. most preferablyof from 30 to 100 nm, 40 to 100 nm, 40 to 90 nm. The layer may be lessthan 500 nm, for example, less than 450, 400, 350, 300, 250, 200, 150,100 nm.

Preferably, the method comprises applying a polymer coating having auniformity variation of less than 10%.

Preferably, the method includes applying a polymer coating having auniformity variation of the contact angles for water of less than 100and a uniformity variation of the oil repellency of less than 0.5according to ISO14419.

In the current invention, superhydrophobic surfaces can be created withcontact angles for water of more than 100°, say 101, 102, 103, 104, 105,106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119 or1200. The same coatings are superoleophobic with oil repellency levelsabove or above and including 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5 or 8for example up to 6 according to ISO14419, say up to or up to andincluding 4, 4.5, 5, 5.5, 6, 6.5, 7 7.5, or 8.

Preferably, the method includes the step of depositing a polymer coatinghaving a contact angle for water of 100° or more and/or an oilrepellency level of 3, 4 or more according to ISO14419 in a residencetime in the plasma zone of approximately 2 minutes or less.

Preferably, the method includes the step of depositing a polymer layerhaving a thickness of approximately 30 nm in a residence time in theplasma zone of approximately 1 minute or less.

Preferably, the method includes the step of depositing a polymer layerhaving a thickness of approximately 50 nm in a residence time in theplasma zone of approximately 2 minutes or less.

The method may include drawing a fixed flow of monomer into a plasmachamber using a monomer vapour supply system. A throttle valve inbetween a pump and the plasma chamber may adapt the pumping volume toachieve the required process pressure inside the plasma chamber.

Preferably the throttle valve is closed by more than 90% (i.e. to reducethe effective cross section in the supply conduit to 10% of its maximumvalue) in order to reduce the flow through the chamber and to allow themonomer to become evenly distributed throughout the chamber.

Once the monomer vapour pressure has stabilized in the chamber theplasma is activated by switching on one or more radiofrequencyelectrodes.

Alternatively, the method may include introducing the monomer into theplasma chamber in a first flow direction; and switching the flow to asecond direction after a predetermined time, for example from 10 to 300seconds, for example from 30 to 240, 40 to 180 seconds, for example lessthan 180, 170, 160, 150, 140, 130, 120, 110, 100, 90, 80, 70, 60, 50,40, 30 or 20 seconds to a second flow direction.

Preferably, further switching of the monomer flow direction may beexecuted, e.g. flow may be switched back to the first flow direction orto one or more further flow directions.

Preferably, monomer may enter the plasma chamber in the first flowdirection for between 20 to 80% of a single process time or 30 to 70% ofthe time or 40 to 60% of the time or 50% of the time.

Preferably, the monomer may enter the plasma chamber in the second flowdirection for between 20 to 80% of a single process time or 30 to 70% ofthe time or 40 to 60% of the time or 50% of the time.

Preferably, the first and second flow directions flow in substantiallyopposite directions. For instance, during a process, monomer may beintroduced into the plasma chamber via walls or inlets which aresubstantially opposite to each another.

Advantages of the inventive method include, but are not limited to, oneor more of allowing highly reactive classes of monomer to polymeriseunder low power continuous wave conditions; generating a benign plasma;adaptable design of the plasma zone and number of electrodes to optimizethe process speed for improved implementation in productionenvironments; providing a means for accurately controlling thetemperature to avoid undesirable temperature gradients; adaptabletension on load cells and variable driving of the rollers for optimalwinding of the material; adaptable design of the unwinding and windingup zone depending on the dimensions and weight of the roll of textilematerial to be coated.

Advantages of the inventive polymer coating include, but are not limitedto, improved hydro- and oleophobic properties of the coated textile;improved functionality of the coated textile; improved adhesion;improved durability of the coated textile and maintained electrostaticcharge in time and in case of contact with discharging liquids such asisopropanol for electrostatically charged filtration textiles, e.g.electrets.

A second aspect of the present invention provides a fabric, e.g. atextile material, having a polymer coating obtainable by contacting afabric with a monomer and subjecting the monomer to low power plasmapolymerisation, wherein the monomer comprises the general formula (I),and wherein n is 2 to 6, m is 0 to 9, X and Y are H, F, Cl, Br or I, R₁is H or alkyl, e.g. —CH₃, or a substituted alkyl, e.g. an at leastpartially halo-substituted alkyl, and R₂ is H or alkyl, e.g. —CH₃ or asubstituted alkyl, e.g. an at least partially halo-substituted alkyl.

Preferably, the fabric is a sheet of fabric, e.g. wound to a roll.

Preferably, the fabric is one of a woven, nonwoven, knitted, film, foilor membrane fabric.

Woven, nonwoven and knitted fabrics may have smooth surfaces or texturedsurfaces, in the cases of a pile weave or a pile knit for example.

Preferably the fabric comprises a synthetic material, a natural materialor a blend.

Examples of materials include but are not limited to:

-   Synthetic: polypropylene (PP), polyethylene (PE), polyvinylchloride    (PVC), polystyrene (PS), polyphenylene sulfide (PPS),    polyacrylonitrile (PAN), polyurethane (PUR), polyurea,    polytetrafluoroethylene (PTFE) and expanded polytetrafluoroethylene    (ePTFE), polyester (PES)—such as polyethylene terephthalate (PET),    recycled PET and polybutylene terephthalate (PBT), polyamide    (PA)—such as PA6, PA66, and PA12, polyaramide, elastane    (polyurethane-polyurea copolymer).-   Natural and man-made: cotton, cellulose, cellulose acetate, silk,    wool, etc.-   Blends: cotton/PES 50:50, PES/carbon 99:1, recycled PES/elastane    92:8, etc. Woven and knitted fabrics may have a thickness of from 50    μm to 5 mm. Nonwoven fabrics may have a thickness of from 5 μm to    5 mm. Film or foil fabrics may have a thickness of from 20 μm to 1    mm.

Preferably, the polymer coating has a thickness of from 10 to 500 nm,e.g. from 10 to 250 nm, e.g. from 30 to 100 nm, e.g. from 40 to 90 nm.

Preferably, the polymer coating comprises superhydrophobic and/orsuperoleophobic properties. Preferably, the superhydrophobic polymercoating has a contact angle for water of 100° or more, say 101, 102,103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116,117, 118, 119 or 1200°. Preferably, the superoleophobic polymer coatingcomprises an oil repellency level above or above and including 3, 3.5,4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5 or 8, for example up to 6 according toISO14419, say up to or up to and including 4, 4.5, 5, 5.5, 6, 6.5, 7,7.5 or 8.

In a third aspect, the invention provides for the use of a monomer toform a polymer coating on a fabric, e.g. a textile material, when themonomer is brought into contact with the fabric and the monomer issubjected to low power plasma polymerisation, wherein the monomercomprises the general formula (I), and wherein n is 2 to 6, m is 0 to 9,X and Y are H, F, Cl, Br or I, R₁ is H or alkyl, e.g. —CH₃, or asubstituted alkyl, e.g. an at least partially halo-substituted alkyl,and R₂ is H or alkyl, e.g. —CH₃ or a substituted alkyl, e.g. an at leastpartially halo-substituted alkyl.

In a further aspect, the invention provides a plasma chamber for coatinga sheet of fabric, e.g. a textile material, with a polymer layer, theplasma chamber comprising a plurality of electrode layers arrangedsuccessively within the plasma chamber, wherein at least two adjacentelectrode layers are radiofrequency electrode layers or at least twoadjacent electrode layers are ground electrode layers.

In another aspect of the present invention, there is provided a plasmachamber for coating a sheet of fabric, such as a textile material, witha polymer layer, the plasma chamber having a plurality of electrodelayers each having a generally planar or plate like form arrangedsuccessively within the plasma chamber, wherein at least two adjacentelectrode layers are radiofrequency electrode layers or ground electrodelayers.

Preferably, the at least two adjacent electrode layers areradiofrequency electrode layers.

Preferably, the outer pair of electrode layers are ground electrodelayers.

In another aspect of the present invention, there is provided a plasmachamber having at least two pairs of electrode layers, and wherein theouter pair of electrode layers are either ground electrode layers orradiofrequency electrode layers.

Preferably, the plasma chamber comprises a pair of radiofrequencyelectrode layers and a pair of ground electrode layers, e.g. having thearrangement M/RF/RF/M or RF/M/M/RF, where ‘M’ denotes a groundelectrode, ‘RF’ denotes a radiofrequency electrode, and wherein ‘/’denotes the positions where the fabric passes between the electrodelayers.

Preferably, the plasma chamber comprises further pairs of radiofrequencyor ground electrode layers, e.g. having the arrangement RF/M/RF/RF/M/RFor M/RF/M/M/RF/M or M/RF/M/RF/RF/M/RF/M or RF/M/RF/M/M/RF/M/RF orRF/M/RF/M/RF/RF/M/RF/M/RF or M/RF/M/RF/M/M/RF/M/RF/M orM/RF/M/RF/M/RF/RF/M/RF/M/RF/M or RF/M/RF/M/RF/M/M/RF/M/RF/M/RF and soon.

In an alternative embodiment, the plasma chamber may comprise a firstelectrode set and a second electrode set, the first and second electrodesets being arranged either side of a passage for receiving a fabric.

Preferably, one or both of the first and second electrode sets comprisean inner electrode layer and a pair of outer electrode layers.

Preferably, the inner electrode layer is a radiofrequency electrode andthe outer electrode layers are ground electrodes, e.g. having thearrangement M*RF*M/M*RF*M or M*RF*M/M*RF*M/M*RF*M and so on.

Alternatively, the inner electrode layer may be a ground electrode andthe outer electrode layers may be radiofrequency electrodes, e.g. havingthe arrangement RF*M*RF/RF*M*RF or RF*M*RF/RF*M*RF/RF*M*RF and so on.

Preferably, the plasma chamber may include further electrode sets, forexample third, fourth, fifth and sixth electrode sets and so on. Forexample when adding a third electrode set, e.g. M*RF*M/M*RF*M/M*RF*M,the fabric is coated on each side in two passes.

In all embodiments of the invention, where the electrode layer is of theradiofrequency type, the electrode layer may also include heatregulating means, e.g. a hollow portion such as a tube for receiving aheat regulator fluid.

Where the electrode layer is of the ground type, the electrode layerneed not comprise a heat regulating means. Thus, electrode layers ofthis type may simply comprise a planar plate, mesh or otherconfiguration suitable for generating plasma when arranged adjacent to aradiofrequency electrode layer.

The electrode layers are preferably of a planar or plate form. Oneadvantage of such a configuration is that the generated plasma issubstantially even across the surface of the electrode set.Consequently, the rate of polymerisation of monomer onto the substrateis the same at any given point on the substrate resulting in increaseduniformity and so on.

Preferably, the heat regulating means comprises tubing which follows apath which curves upon itself by approximately 1800 at regular intervalsto provide an electrode that is substantially planar in dimension.

Preferably, the heat regulating means comprises a diameter of fromapproximately 2.5 to 100 mm, more preferably from approximately 5 to 50mm, even more preferably from approximately 5 to 30 mm, say up to 25, 20or 15 mm, for example 10 mm.

Preferably, the heat regulating means has a wall thickness of fromapproximately 0.1 to 10 mm, more preferably from approximately 0.25 to 5mm, even more preferably from approximately 0.25 to 2.5 mm, say 1.5 mm.

Preferably, the distance between the heat regulating means before andafter the curve is between 1 and 10 times the diameter of the heatregulating means, say around 3 to 8, for example 5 times the diameter ofthe heat regulating means.

Preferably, the heat regulating means comprises a conductive materialsuch as a metal, e.g. aluminium, stainless steel or copper. Othersuitable conductive materials may be envisaged.

Preferably, the or each radiofrequency electrode generates a highfrequency electric field at frequencies of from 20 kHz to 2.45 GHz, morepreferably of from 40 kHz to 13.56 MHz, with 13.56 MHz being preferred.

Preferably, the plasma chamber further comprises locating and/orsecuring means such as one or more connecting plates and/or the chamberwalls for locating each electrode or each electrode set at a desiredlocation with the plasma chamber.

Preferably, the locating and/or securing means is removable from theplasma chamber, e.g. the locating and/or securing means is slidablyremovable from the plasma chamber.

Preferably, the plasma chamber comprises one or more inlets forintroducing a monomer to the plasma chamber.

Preferably, each inlet feeds monomer into a monomer distribution systemthat distributes the monomer evenly across the chamber. For example, themonomer inlet may feed into a manifold which feeds the chamber.

Preferably the evaporated monomer is able to strike the plasma andthereby substantially obviates the need to use an inert gas, such ashelium, nitrogen or argon, as a carrier gas.

However, Applicant found that in some cases the addition of a smallamount of carrier gas leads to better stability of the plasma inside theplasma chamber, thereby providing a more uniform thickness of thecoating layer. The ratio of carrier gas to monomer is preferably equalto or less than 1:4.

Preferably the carrier gas is an inert gas such as helium or argon.

Preferably the carrier gas and the monomer are mixed together beforeentering the process chamber, to provide an improved mixture of thecarrier gas and the monomer prior to processing.

The apparatus also includes a monomer vapour supply system. Monomer isvaporized in a controlled fashion. Controlled quantities of this vapourare fed into the plasma chamber preferably through a temperaturecontrolled supply line.

Preferably, the monomer is vaporized at a temperature in the range of50° C. to 180° C., more preferably in the range of 100° C. to 150° C.,the optimum temperature being dependent on the physical characteristicsof the monomer. At least part of the supply line may be temperaturecontrolled according to a ramped (either upwards or downwards)temperature profile. The temperature profile will typically have a lowend which is at a higher temperature than the point where the monomer isvaporized towards the end of the supply line. In the vacuum chamber themonomer will expand and the required temperatures to preventcondensation in the vacuum chamber and downstream to the pump willtypically be much lower than the temperatures of the supply line.

In those situations where small amounts of carrier gas are used, thecarrier gas can be delivered from a gas bottle, a tank or reservoir. Itsflow rate is regulated by a mass flow controller. After passing the massflow controller, the carrier gas is fed into the monomer supply line,with the monomer already having passed a flow controller in order tohave established a stable monomer flow and a stable carrier gas flow.

It is preferable that a minimum distance of a few mm, more preferably 10to 100 mm, for example 10 to 90 mm, say less than 80, 70, 60 or 50 mm,most preferably 15 to 50 mm, is maintained between the electrodes andthe surface of the fabric to be coated.

Preferably, the plasma chamber also includes a plurality of rollers forguiding a sheet of fabric, in use, between each electrode layer.

Preferably, the rollers are heated to avoid the presence of cold spotswhere the monomer could condense. Preferably the rollers are heated fromroom temperature of approximately 20 to 85° C., more preferably from 25to 70° C., for example 30 to 60° C. Preferably the rollers are heated bywater, oil or other liquids or combinations thereof, most preferablywater. Preferably the rollers are provided with a temperature controlmeans to regulate the temperature to avoid significant temperaturedifferentials.

Preferably the rollers can be divided in two categories: load cells andnormal rollers. For rigid textile materials, such as thick films orfoils, the rollers do not need to be driven individually. It issufficient for the winding up roller to be driven at a certain speed,and all other rollers will start rolling because of the winding upmovement.

For more fragile materials, such as apparel textile and filtrationmaterials, most or all rollers are driven individually to avoid damageof the fabric or material or a rupture of the sheet of textile materialdue to excessive tensions. Preferably, for the most fragile materials,e.g. membranes or thin open structured nonwovens, the rollers are alldriven individually and can be fine-tuned individually or as a groupe.g. to optimise the processing of fragile textile materials.

Preferably the plasma chamber has one or more load cells that can becalibrated once a predetermined low base pressure is reached and priorto the first processing step and before any unwinding or winding of thefabric on the rolls, e.g. prior to outgassing, or prior to the gas inletand prior to turning on the electromagnetic field for a pre-treatment,or prior to the gas inlet and prior to turning on the electromagneticfield for the coating step, whichever comes first.

The load cells are not driven but provide a certain tension on the sheetof fabric to be coated. The tension needs to be selected according tothe material type. For more fragile materials, and certainly for themost fragile materials, the applicant found that for each individualcoating run after closing the machine and pumping down to base pressure,a calibration of all load cells improves the winding and coatingquality.

Preferably prior to each individual coating run, the load cells arecalibrated once the base pressure is reached and prior to the firstprocessing step.

Preferably, during the coating process, the system runs at a speed of0.1 m/min up to 20 m/min, for example 0.5 m/min to 15 m/min, such as 1m/min to 10 m/min, say less than 9, 8, 7, 6 m/min, most preferably 1 to5 m/min.

Preferably, the tension at which the fabric is wound is 0.2 to 250 kg (2to 2500 N), more preferably 0.5 to 100 kg (5 to 1000 N), for example 1to 50 kg (10 to 500 N), such as 1.5 to 25 kg (15 to 250 N), such as 1.5to 10 kg (15 to 100 N).

Preferably, for rolls with limited outer diameter, weight and width, theunwinding zone and the winding up zone are positioned at the same sideof the plasma chamber, wherein the unwinding starts in the lower part ofthe winding zone and the winding up takes place in the upper part.

Preferably, for rolls that are heavy, and/or have a large outer diameterand/or that are wide, e.g. 2 m wide, the unwinding and winding up takeplace at different sides of the plasma chamber, e.g. the unwinding atthe left side and the winding up at the right side.

In a further aspect, the invention provides a method for coating a sheetof fabric, e.g. a textile material, with a polymer layer, the methodcomprising the steps of providing a plasma chamber having a plurality ofelectrode layers arranged successively within the plasma chamber,wherein at least two adjacent electrode layers are radiofrequencyelectrode layers or ground electrode layers; and guiding a sheet offabric between said electrode layers.

Preferably, the method includes the step of regulating the temperatureof each radiofrequency electrode layer, e.g. from approximately 5 to200° C.

Preferably, the method includes the step of regulating the temperatureof each radiofrequency electrode layer from approximately 20 to 90° C.,more preferably from approximately 25 to 60° C., even more preferablyfrom approximately 30 to 40° C.

Preferably, the step of regulating the temperature of eachradiofrequency electrode layer comprises feeding a heat regulating meanswith a fluid such as a liquid such as water, oil or other liquids orcombinations thereof.

Preferably, the method includes the step of controlling the temperatureof the plasma chamber, e.g. to avoid temperature differentials withinthe chamber, and to avoid cold spots where the process gas can condense.For instance, the door, and some or each wall(s) of the plasma chambermay be provided with temperature control means.

Preferably, the temperature control means maintains the temperature fromroom temperature of approximately 20 to 70° C., more preferably frombetween 30 and 50° C.

Preferably, also the pump, the liquid monomer supply and all connectionsbetween those items and the plasma chamber are temperature controlled aswell to avoid cold spots where the process gas or gases can condense.

Preferably, the method comprises the step of applying power across theradiofrequency electrodes via one or more connecting plates.

The power for the plasma may be applied in either low power continuouswave mode or pulsed wave mode.

Preferably, when applied in continuous wave mode in a 9000 l chamber,the applied power is approximately 5 to 5000 W, more preferablyapproximately 10 to 4000 W, even more preferably approximately, say 25to 3500 W, even further preferably, for example 30 to 3000 W, preferablystill, for example 40 to 2500 W, and even further preferably from 50 to2000, 1900, 1800, 1750, 1700, 1600, 1500, 1400, 1300, 1250, 1200, 1100,1000, 950, 900, 850, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350,300, 250, 200, 175, 150, 125, 100, 90, 80, 75, 70, or 60 W.

Preferably, when applied in pulsed wave mode in a 9000 l chamber, theapplied power is approximately 5 to 5000 W, more preferablyapproximately 25 to 4000 W, even more preferably approximately 50 to3500 W, preferably, for example 75 to 3000 W, preferably still, forexample 100 to 2500 W, and even further preferably from 150 to 2000,1900, 1800, 1750, 1700, 1600, 1500, 1400, 1300, 1250, 1200, 1100, 1000,950, 900, 850, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350, 300,250, 200, or 175 W.

When applied in pulsed power mode, the pulse repetition frequency may befrom 100 Hz to 10 kHz having a duty cycle from approximately 0.05 to50%, with the optimum parameters being dependent on the monomer used.

Although the preferred applied power might seem to be high, thoseskilled in the art will understand that a large plasma chamber, such asone of 9000 liter capacity, will include more and larger radiofrequencyelectrodes compared to machines in which small sheets of textile arecoated instead of rolls. As a consequence the power is increased to forma uniform and stable plasma. But, compared to prior art gaseousprecursor monomers, the inventive coating is deposited at low power.Prior art coatings deposited using gaseous precursors require an appliedpower of 5000 W or more, up to 10000 W and even up to 15000 W, dependingon the dimensions and the number of electrodes.

Preferably, the radiofrequency electrode or electrodes generate a highfrequency electric field at frequencies of from 20 kHz to 2.45 GHz, morepreferably of from 40 kHz to 13.56 MHz, with 13.56 MHz being preferred.

Preferably, the step of guiding a sheet of fabric between said electrodelayers involves the use of a plurality of rollers.

As used herein, the term “adjacent electrode layers” is intended torefer to a pair of electrode layers, whereby one of the pair isdisposed, in use, on one side of a sheet of fabric and the other of thepair is disposed on the obverse side of the sheet of fabric.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood, it will nowbe described by way of example only and with reference to theaccompanying drawings, in which:

FIG. 1 shows a schematic representation of a roll-to-roll plasmadeposition apparatus;

FIG. 2 shows a first electrode arrangement according to the prior art;

FIG. 3 shows a second electrode arrangement according to the prior art;

FIG. 4 shows a first electrode arrangement according to the presentinvention;

FIG. 5 shows a second electrode arrangement according to the presentinvention;

FIG. 6 shows a third electrode arrangement according to the presentinvention;

FIG. 7 shows a fourth electrode arrangement according to the presentinvention; and

FIG. 8 shows plan (a), side (b) and end (c) views of a radiofrequencyelectrode.

FIG. 9 is a graph showing results of water absorption in an uncoatedmaterial after one minute, one hour and twenty-four hours drip-out.

FIG. 10 shows oil repellency as a number of washing cycles.

FIG. 11 shows spray test results related to numbers of washing cycle.

FIG. 12 shows oil repellency with and without pretreatment compared tonumbers of wash cycles.

FIG. 13 shows spray test results from a number of washing cycles.

FIG. 14 shows oil repellency in a function of numbers of Martindaleabrasion cycles.

FIG. 15 shows spray test results in a function of numbers of Martindaleabrasion cycles.

DETAILED DESCRIPTION

Referring first to FIG. 1 a roll-to-roll plasma deposition apparatus,indicated generally at 1, will now be described. The apparatus 1comprises a plasma chamber 10, a first compartment 12 and a secondcompartment 14. The first 12 and second 14 compartments are theunwinding and winding up compartments, arranged at both sides of theplasma chamber. These compartments are known to those skilled in the artand will not be described in any further detail.

The plasma chamber 10 comprises an array of electrode layers RF, M, thearrangement of which will be described in detail further below withreference to FIG. 4. The plasma chamber 10 further comprises a series ofupper and lower rollers 101, 102 and load cells for guiding a sheet oftextile material 16 between the electrode layers RF, M from a first roll120 mounted in the first compartment 12 to a second roll 140 mounted inthe second compartment 14.

Schematic diagrams of electrode layer arrangements according to theprior art are shown in FIGS. 2 and 3. The most basic arrangement isshown in FIG. 2 in which a radiofrequency electrode layer and a groundelectrode layer are arranged in a side-by-side relationship. Thisarrangement may be symbolized as M/RF, where ‘M’ denotes a groundelectrode, ‘RF’ denotes a radiofrequency electrode, and ‘/’ denotes thespace in which the textile material 16 passes. Upper 101 and lower 102rollers are arranged to guide a sheet of the textile material 16 fromone roll 120 to another roll 140. In use, and when an electromagneticfield is applied to the radiofrequency electrode layer RF, plasma isstruck between the radiofrequency electrode layer RF and the groundelectrode layer M. Such plasma is known as primary plasma. When monomeris present in the plasma chamber 10 this results in a polymer coatingbeing applied to a surface of the sheet of textile material 16 that isfacing the radiofrequency electrode layer RF, resulting in a sheet oftextile material 16 having a uniform polymer coating applied to a singlesurface thereof.

FIG. 3 shows a further arrangement in which additional radiofrequencyelectrode layers RF and ground electrode layers M are arrangedalternately in a side-by-side relationship. This arrangement may besymbolized as M/RF/M/RF/M. Again, primary plasma is struck between aradiofrequency electrode layer RF and a ground electrode layer M suchthat a polymer coating is applied to a surface of the sheet of textilematerial 16 that is facing the radiofrequency electrode layer RF. Thesheet of textile material 16 makes four passes and on each pass the sameside of the textile material 16 facing the radiofrequency electrodelayer RF is coated, resulting in a sheet of textile material 16 having auniform polymer coating applied to a single surface thereof.

In a first embodiment of the invention the electrode arrangementcomprises ten electrode layers arranged in sequence as shown in FIG. 4.This arrangement may be symbolized as M/RF/M/RF/M/M/RF/M/RF/M (thisrepresents the arrangement as shown in FIG. 1). In use, and when anelectromagnetic field is applied to the radiofrequency electrode layers,plasma is struck between the electrode layers. A primary plasma isstruck between a radiofrequency electrode layer RF and a groundelectrode layer M. Therefore, whilst it is clear that the sheet oftextile material 16 makes nine passes between the electrode layers, onlythe first and last four passes are through primary plasma zones.

Accordingly, during the first four passes monomer is polymerised onto afirst side of the sheet of textile material 16 whilst during the lastfour passes monomer is polymerised onto the obverse side of sheet oftextile material 16, resulting in a sheet of textile material 16 havinga uniform polymer coating applied to each surface thereof. During thefifth pass an insignificant quantity to no monomer is deposited onto thesheet of textile material 16.

FIG. 5 shows a second simplified embodiment of the invention in whichthe electrode arrangement comprises four electrode layers arranged insequence. This arrangement may be symbolized as M/RF/RF/M. In use, andwhen an electromagnetic field is applied to the radiofrequency electrodelayer, plasma is struck between the electrode layers. A primary plasmais struck between a radiofrequency electrode layer RF and a groundelectrode layer M. Therefore, whilst it is clear that the sheet oftextile material 16 makes three passes between the electrode layers,only the first and third passes are through primary plasma zones.Accordingly, during the first pass monomer is polymerised onto a firstside of the sheet of textile material 16 whilst during the third passmonomer is polymerised onto the obverse side of the sheet of textilematerial 16, resulting in a sheet of textile material 16 having auniform polymer coating applied to each surface thereof. During thesecond pass an insignificant quantity to no monomer is deposited ontothe sheet of textile material 16.

In a third embodiment the electrode layers may be arranged as follows:RF/M/M/RF. Similarly, when an electromagnetic field is applied to theradiofrequency electrode layers, plasma is struck between the electrodelayers. A primary plasma is struck between a radiofrequency electrodelayer and a ground electrode layer. Therefore, whilst it is clear thatthe sheet of textile material 16 makes three passes between theelectrode layers, only the first and third passes are through primaryplasma zones. Accordingly, during the first pass monomer is polymerisedonto a first side of the sheet of textile material 16 whilst during thethird pass monomer is polymerised onto the obverse side of the sheet oftextile material 16, resulting in a sheet of textile material 16 havinga uniform polymer coating applied to each surface thereof. During thesecond pass an insignificant quantity to no monomer is deposited ontothe sheet of textile material 16.

The applicant has surprisingly discovered that the polymer coating hasgreater uniformity, as found when measurements were made in testing e.g.in contact angles for water and/or greater uniformity in oil repellency,when the ground electrode layers are placed at the outer positions asdescribed in the first and second embodiments.

In order to coat each side of the fabric the applicant has discoveredthat it is important to have a pair of identical electrode layersside-by-side in the series. For instance a pair of ground electrodelayers, as described in the first or third embodiments, or a pair ofradiofrequency electrode layers, as described in the second embodiment.This inventive arrangement results in the switching of polymerdeposition from one side of the sheet of textile material 16 to another.

In further embodiments additional arrangements may be envisaged. Forinstance, RF/M/RF/RF/M/RF or M/RF/M/M/RF/M. In these embodiments it isclear that the sheet of textile material 16 makes five passes betweenthe electrode layers: the first, second, fourth and fifth passes beingthrough primary plasma zones. Accordingly, during the first and secondpasses monomer is polymerised onto a first side of the sheet of textilematerial 16 whilst during the fourth and fifth passes monomer ispolymerised onto the obverse side of the sheet of textile material 16,resulting in a sheet of textile material 16 having a uniform polymercoating applied to each surface thereof. During the third passinsignificant to no monomer is deposited onto the sheet of textilematerial 16.

Similarly, even further embodiments are envisaged having additionalelectrode layers incorporated into the sequence, e.g.M/RF/M/RF/RF/M/RF/M or RF/M/RF/M/M/RF/M/RF or RF/M/RF/M/RF/RF/M/RF/M/RFor M/RF/M/RF/M/M/RF/M/RF/M or M/RF/M/RF/M/RF/RF/M/RF/M/RF/M orRF/M/RF/M/RF/M/M/RF/M/RF/M/RF and so on. As the number of electrodelayers increases in the series so does the number of passes through aprimary plasma zone. Accordingly, it is possible to control thethickness of the resultant polymer layer by increasing or decreasing thenumber of electrode layers in the sequence. Also, by increasing thenumber of electrode layers in the sequence it is possible to increasethe speed within which the sheet of textile material 16 passes throughthe plasma chamber 10 without compromising on the quality of the polymerlayer.

In a further embodiment shown in FIG. 6 the electrode layers arearranged as follows: M*RF*M/M*RF*M, where ‘RF’ denotes a radiofrequencyelectrode layer, ‘M’ denotes a ground electrode layer, ‘*’ denotes aprimary plasma zone and ‘/’ denotes the space in which the fabricpasses. In this embodiment the plasma chamber 10 comprises a firstelectrode set (M*RF*M) and a second electrode set (M*RF*M), wherein thefirst and second electrode sets comprise electrode layers and whereineach electrode set comprises two ground electrode layers M and a singleradiofrequency electrode layer RF. In this embodiment it is clear thatthe sheet of textile material 16 makes a single pass between theelectrode sets (M*RF*M).

Although we neither wish nor intend to be bound by any particulartheory, we understand that the plasma created in between electrode sets(M*RF*M) of this embodiment of the invention cannot be described aseither a pure primary or as a pure secondary plasma. Rather, theinventors consider that the electrode sets (M*RF*M) create a new hybridform of plasma which is strong enough to start and maintain apolymerisation reaction at very low power, but which at the same time isbenign enough not to break down the reactive monomers. Accordingly,during the first pass monomer is polymerised onto first and second sidesof the sheet of textile material 16, resulting in a sheet of textilematerial 16 having a uniform polymer coating applied to each surfacethereof.

The processing speeds may be increased by adding further electrode sets(M*RF*M) to the plasma chamber 10, for example third, fourth, fifth andsixth electrode sets (M*RF*M) and so on. For example when adding a thirdelectrode set (M*RF*M), the sheet of textile material 16 is coated onboth sides in two passes, e.g. M*RF*M/M*RF*M/M*RF*M orRF*M*RF/RF*M*RF/RF*M*RF. FIG. 7 shows an example of an electrodearrangement having six electrode sets (M*RF*M) arranged in sequence. Inthis design, contrary to FIG. 1, the unwinding and the winding up takeplace in the same area at the same side of the plasma chamber.

FIG. 8 shows a radiofrequency electrode layer RF in plan (a), side (b)and end (c) views. The radiofrequency electrode layer RF comprises agenerally planar body formed from folded tubing 21. The tubing 21 maycomprise a plurality of sections which are joined together by connectors27. The tubing 21 is typically formed of a conductive metallic materialsuch as aluminium, stainless steel or copper. The tubing 21 is hollow toallow for a temperature regulation fluid to be passed through theelectrode layer RF to regulate the plasma at a predeterminedtemperature. The tubing 21 comprises a series of bends 22 formed atregular intervals along the tubing length. The tubing 21 curves back onitself at each bend 22 by approximately 180°. The tubing 21 has adiameter of approximately 10 mm and a wall thickness of approximately 2mm. The distance between the tubing 21 before and after each bend 22 isapproximately 5 times the diameter of the tubing 21.

The tubing 21 is curved at each end so as to provide distal portions 25,26 which are substantially orthogonal to the planar body. The distalportions 25, 26 may be connected to a fluid supply or egress line (notshown). Alternatively, the distal portions 25, 26 may be connected tothe distal portions of adjacent or nearby electrode layers.

The radiofrequency electrode layer RF further comprises a pair ofconnecting plates 23, 24 attached to the front and to the rear of theelectrode layer 20 adjacent to the bends 22. The connecting plates 23,24 provide both a means for attaching the radiofrequency electrode layerRF to the inside of the vacuum chamber 11 and electrical contacts forapplying a load thereto.

A ground electrode layer M (not shown in detail) typically comprises aplanar sheet of aluminium.

An example sequence of depositing a polymer coating to a roll of fabricis as follows:

-   -   1. A roll of fabric 120 to be treated is mounted in a first        compartment 12 of the apparatus 1;    -   2. The free end of the fabric 16 is fed (manually or        automatically) through the rollers 101, 102 within the plasma        chamber 10 and then secured to an empty roll 140 in a second        compartment 14;    -   3. The plasma chamber 10 is closed and the electrodes, which are        mounted on the moving part of the machine, are slid in between        the guiding rolls (and thus in between the textile);    -   4. The plasma chamber 10 is sealed and pumped down to the        required predetermined base pressure;    -   5. The load cells are calibrated for optimal processing;    -   6. Gas inlet valve is opened and the evaporated liquid monomer        is fed into the plasma chamber 10 in a controlled manner at a        controlled rate;    -   7. An electromagnetic field is applied to the radiofrequency        electrode layers RF and a low power continuous wave plasma is        generated;    -   8. Power is applied to the rollers 101, 102 of the apparatus 1        in order to unwind fabric 16 from first roll 120, and wind it        onto a second roll 140, during which time it passes between the        electrode layers RF, M or sets of electrode layers M*RF*M,        RF*M*RF where a polymer coating is deposited to each side of the        fabric 16 before being wound onto second roll 140;    -   9. Once all of the fabric 16 has had a polymer coating applied        thereto, the electromagnetic field is turned off and the plasma        chamber 10 is ventilated to atmospheric pressure.        A second example sequence of depositing a polymer coating to a        roll of fabric, e.g. in a 9000 l chamber, is as follows:    -   1. A roll of fabric 120 to be treated is mounted in a first        compartment 12 of the apparatus 1;    -   2. The free end of the fabric 16 is fed (manually or        automatically) through the rollers 101, 102 within the plasma        chamber 10 and then secured to an empty roll 140 in a second        compartment 14;    -   3. The plasma chamber 10 is closed and the guiding rolls and all        the textile (on roll in the unwinding area, the free end of the        fabric mounted on a core in the winding up area, and the textile        guided through the guiding rolls), which are mounted on the        moving part of the machine, are slid in between the electrodes;    -   4. The plasma chamber 10 is sealed and pumped down to a        predetermined base pressure required for outgassing and        pre-treatment;    -   5. The load cells are calibrated for optimal processing;    -   6. The gas inlet valve is opened and the inert gas for the        pre-treatment, e.g. cleaning and/or activation and/or etching,        which is combined with further gassing out of the textile prior        to coating, is fed into the plasma chamber 10;    -   7. An electromagnetic field is applied to the radiofrequency        electrode layers RF and a plasma is generated; this plasma may        be either a continuous wave plasma or a pulsed wave plasma, the        choice of plasma mode being dependent upon the required power        level and determined to be optimum for the pre-treatment gas or        gases used and/or for the size and design of the plasma        equipment and/or for a particular textile being used;    -   8. Power is applied to the rollers 101, 102 of the apparatus 1        in order to unwind fabric 16 from first roll 120, and wind it        onto a second roll 140, during which time it passes between the        electrode layers RF, M or sets of electrode layers M*RF*M,        RF*M*RF where moisture is removed from fabric 16 and where each        side of the fabric 16 is pre-treated before being wound onto        second roll 140;    -   9. Once all of the fabric 16 has been gassed out and        pre-treated, the electromagnetic field is turned off and the        plasma chamber 10 is pumped to the required lower base pressure        for polymer layer deposition;    -   10. Gas inlet valve is opened and the evaporated liquid monomer        is fed into the plasma chamber 10 in a controlled manner at a        controlled rate;    -   11. An electromagnetic field is applied to the radiofrequency        electrode layers RF and a low power plasma is generated; this        plasma may be either a continuous wave plasma or a pulsed wave        plasma, the choice of plasma mode being dependent upon the power        level needed and determined to be optimum for a particular        monomer being used to treat the material being treated and/or        for the size and/or the design of the plasma equipment and/or        for a particular textile being used;    -   12. Power is applied to the rollers 101, 102 of the apparatus 1        and fabric 16 is unwound from roll 140, passes between the        electrode layers RF, M or sets of electrode layers M*RF*M,        RF*M*RF where a polymer coating is deposited to each side of the        fabric 16 before being wound onto roll 120;    -   13. Once all of the fabric 16 has had a polymer coating applied        thereto, the electromagnetic field is turned off and the plasma        chamber 10 is ventilated to atmospheric pressure.

Example 1

An experiment was carried out on small rolls of a textile for use as afiltration media before scaling up to production level. The textilecomprised a nonwoven synthetic material comprising polymer fibres. Theroll was 1000 m long and 1.1 m wide.

The process parameters are presented in Tables 1 and 2.

TABLE 1 Parameter Value Liquid Monomer Supply (LMS) Temperature canister130-150° C. Temperature LMS 140-150° C. Plasma Zone Length of plasmazone 6 m Treatment speed 2 m/min Tension 1.5 kg (15N) Temperature walls40-50° C. Electrodes & Generator Electrode configurationM/RF/M/RF/RF/M/RF/M Plasma type Primary Power 100-500 W Frequency 13.56MHz Frequency mode cw Temperature RF electrode 30-35° C. Monomer1H,1H,2H,2H-Perfluorooctyl acrylate Flow 40-100 sccm Pressure Basepressure 10-50 mTorr Work pressure 20-80 mTorr Residence time in plasma3 minutes zone Oleophobicity Level 5 (ISO 14419-2010)

TABLE 2 Parameter Value Liquid Monomer Supply (LMS) Temperature canister130-150° C. Temperature LMS 140-150° C. Plasma Zone Length of plasmazone 6 m Treatment speed 2 m/min Tension 1.5 kg (15N) Temperature walls40-50° C. Electrodes & Generator Electrode configurationM/RF/M/RF/RF/M/RF/M Plasma type Primary Power 500-1000 W Frequency 13.56MHz Frequency mode pulsed (10²-10⁴ Hz; duty cycle 0.1-20%) TemperatureRF electrode 30-35° C. Monomer 1H,1H,2H,2H-Perfluorooctyl methacrylateFlow 40-100 sccm Pressure Base pressure 10-50 mTorr Work pressure 20-80mTorr Residence time in plasma 3 minutes zone Oleophobicity Level 3 (ISO14419-2010)

The resultant coated textile according to Table 1 demonstrated goodhydro- and oleophobic properties as well as efficient filtration so itwas decided to scale up the process.

The resulting hydro- and oleophobic properties of the textiles coatedwith the process according to Table 2 are lower than from the coatedtextiles according to Table 1. However, it is decided to scale up thisprocess as well.

Example 2

The processes of example 1 were increased in scale. The textile materialwas the same as that of example 1. The roll was 10000 m long and 1.1 mwide.

The process parameters are presented in Tables 3 and 4.

TABLE 3 Parameter Value Liquid Monomer Supply (LMS) Temperature canister130-150° C. Temperature LMS 140-150° C. Plasma Zone Length of plasmazone 12 m Treatment speed 4 m/min Tension 1.5 kg (15N) Temperature walls40-50° C. Electrodes & Generator Electrode configurationM/RF/M/RF/M/RF/RF/M/RF/M/RF/M Plasma type Primary Power 200-800 WFrequency 13.56 MHz Frequency mode cw Temperature RF electrode 30-35° C.Monomer 1H,1H,2H,2H-Perfluorooctyl acrylate Flow 50-120 sccm PressureBase pressure 30-50 mTorr Work pressure 70-90 mTorr Residence time inplasma 3 minutes zone Oleophobicity Level 5 (ISO 14419-2010)

TABLE 4 Parameter Value Liquid Monomer Supply (LMS) Temperature canister130-150° C. Temperature LMS 140-150° C. Plasma Zone Length of plasmazone 12 m Treatment speed 4 m/min Tension 1.5 kg (15N) Temperature walls40-50° C. Electrodes & Generator Electrode configurationM/RF/M/RF/M/RF/RF/M/RF/M/RF/M Plasma type Primary Power 700-1200 WFrequency 13.56 MHz Frequency mode pulsed (10²-10⁴ Hz; duty cycle0.1-20%) Temperature RF electrode 30-35° C. Monomer1H,1H,2H,2H-Perfluorooctyl methacrylate Flow 50-120 sccm Pressure Basepressure 30-50 mTorr Work pressure 70-90 mTorr Residence time in plasma3 minutes zone Oleophobicity Level 3 (ISO 14419-2010)

The resultant coated textile according to Table 3 demonstrated goodhydro- and oleophobic properties as well as efficient filtration. Theresulting hydro- and oleophobic properties of the textiles coated withthe process according to Table 4 are lower than from the coated textilesaccording to Table 3.

Results

Oil Repellency

Examples 1 and 2 show that low power continuous wave plasmapolymerisation processes provide a better performance than pulsed waveplasma polymerisation processes. This is demonstrated by the oilrepellency which is tested according to ISO 14419.

The results are presented in Table 5, and show that the oil repellencyfor continuous wave coatings of A4 sheets is higher than for pulsed wavecoatings, the effect being more pronounced for short treatment times,e.g. 2 minutes.

TABLE 5 Oil repellency for continuous wave and pulsed wave Depositionmode Treatment time (min) Oil repellency Continuous wave (cw) 2 minutesL 6 Pulsed 2 minutes L 3 Continuous wave (cw) 5 minutes L 6 Pulsed 5minutes L 4Filtration Efficiency

The filtration efficiency for standard filtration media and filtrationmedia coated in accordance with the present invention were tested forthree different grades of High Efficiency Particulate Arresting (HEPA)filter elements (grades F7, F8 and F9). Grades F7, F8 and F9 areindications given to secondary filter elements depending on theirefficiency they should reach according to the BS EN 779 test standard.The required efficiency in use (middle efficiency) depends on theparticle size to be filtered.

For 0.4 μm particles, F7 grades should obtain a middle efficiency of80-90%.

For 0.4 μm particles, F8 grades should obtain a middle efficiency of90-95%.

For 0.4 μm particles, F9 grades should obtain a middle efficiency ofmore than 95%.

The filtration of this test media is charged, i.e. to form an electret,and may be used in heating, ventilation or air conditioning (HVAC)systems.

The initial and the middle filtration efficiency for 0.4 μm pores ismeasured according to standard European air filter test BS EN 779 forthe standard filtration media and plasma coated filtration media incharged form and in discharged form. The filtration media is dischargedby bringing into contact with isopropanol.

The initial filtration efficiency is the efficiency of a clean, brandnew filter element. It is obvious that once the filter is in use, itspores become blocked by filtered particles, and by consequence itsefficiency increases during lifetime. The initial efficiency is thus theminimal efficiency.

The results for the first fabric grade F7 are presented in Table 6. Inorder to pass the test the required average efficiency is 80 to 90% andthe initial efficiency is 35% or more.

TABLE 6 Standard Standard Plasma Plasma Type of F7— F7— treated F7—treated F7— filter charged discharged charged discharged Initial 55% 39%70% 64% efficiency 0.4 μm Average 85% — 87% 87% efficiency 0.4 μm

From Table 6 it is clear that the initial filtration efficiency forcharged filter elements coated with an inventive coating is enhanced.Once the filters are discharged, the initial and average efficiency forstandard filters drops highly, while the plasma treated filter elementsdo not show an efficiency drop for the average efficiency and a slightdrop for the initial efficiency.

The results for the second fabric grade F8 are presented in Table 7. Inorder to pass the test the required average efficiency is 90 to 95% andthe initial efficiency is 55%.

TABLE 7 Standard Standard Plasma Plasma Type of F8— F8— treated F8—treated F8— filter charged discharged charged discharged Initial 50% 33%80% 87% efficiency 0.4 μm Average 83% 76% 92% 94% efficiency 0.4 μm

From Table 7 it is clear that the initial and average filtrationefficiency for charged filter elements coated with an inventive coatingis enhanced. Once the filters are discharged, the initial and averageefficiency for standard filters drops, while the plasma treated filterelements do show an efficiency increase for the average efficiency andfor the initial efficiency.

The standard filter elements do not have the required average efficiencyof 90-95%, while the plasma coated filters reach the spec for bothcharged and discharged.

The standard filter elements do not have the required initial efficiencyof 55%, while the plasma coated filters reach the spec for both chargedand discharged.

Filtration efficiency is enhanced for discharged filter elements coatedwith an inventive coating. After discharge with isopropanol, the coatingis still on the filter element preventing the latter from showing adecrease in efficiency.

Penetration of Dispersed Oil Particles (DOP)

Respirator masks having five layers of nonwoven meltblown polypropylene(15-30 g/m²) are electrostatically charged after coating with a coatingaccording to Example 1. Evaluation of the penetration is done using aCertitest 8130 apparatus loading the textile with 200 mg ofDOP-particles. The results are presented in Table 8.

TABLE 8 Initial Penetration penetration after (x) Filter mediumConditioning (%) minutes (%) Supplier I—28 g/m² Uncoated 1.20 6.40 (30)Supplier I—28 g/m² Plasma coated 0.48 1.08 (30) Supplier I—22 g/m²Uncoated 1.25 3.90 (10) Supplier I—22 g/m² Plasma coated 0.40 0.75 (10)Supplier II—25 g/m² Uncoated N.A. N.A. Supplier II—25 g/m² Plasma coated0.02 0.03 (10)

It is clear from Table 8 that the plasma coated materials perform muchbetter than the uncoated reference materials. The initial penetration isabout 3 times less; the penetration after 10 to 30 minutes is 5 to 6times less. The filtration efficiency for oily particles is enhanced byusing an inventive coating.

Filter Efficiency

Diesel filters made of approximately 1 to 2 mm thick nonwovenpolyethylene terephthalate (PET) of 500 g/m² are coating with aninventive coating according to Example 2.

The efficiency is tested by soaking the filter elements in water for 22hours, followed by a drip out of a certain time (minute range) invertical position. The weight increase is calculated and compared tonon-coated reference samples of the same material.

The results are presented in the following graph.

From the graph shown in FIG. 9, it is clear that uncoated materialabsorbs a high volume of water, almost 1800% weight increase after 1minute drip out.

Samples coated with an inventive coating show extremely low waterabsorption values, less than 10% weight increase after 1 minute dripout.

Washability

Three different polyester woven fabrics coated with a low power plasmacoating according to Table 3 from Example 2 have been washed accordingto ISO 15797 (2002).

One complete washing cycle comprised the following steps:

-   -   1. Washing at 60° C. and using 20 g IPSO HF 234 without optical        whitener per kilogram dry textile material;    -   2. Tumble drying;    -   3. Hot pressing at 180° C. (e.g. ironing).

Five washing cycles have been performed one after the other, then theoil repellency was measured according to ISO 14419 and a spray test wasperformed according to ISO 9073—part 17 and ISO 4920.

Next, five more washing cycles have been done and the oil repellencytest and spray test have been repeated.

The oil repellency in function of the number of washing cycles ispresented in FIG. 10. FIG. 11 shows the spray test results in functionof the number of washing cycles.

In a further example another polyester woven fabric has been coated withand without a pre-treatment prior to the coating step. The processwithout pre-treatment is carried out according to Example 1.

The process parameters for the process with pre-treatment are presentedin Table 9.

TABLE 12 Parameter Value Pre-treatment Gas Argon Flow 500-1000 sccmTreatment speed 6 m/min Power 500-750 W Frequency 13.56 MHz Frequencymode cw Liquid Monomer Supply (LMS) Temperature canister 130-150° C.Temperature LMS 140-150° C. Plasma Zone Length of plasma zone 6 mCoating step speed 2 m/min Tension 1.5 kg (15N) Temperature walls 40-50°C. Electrodes & Generator Electrode configuration M/RF/M/RF/RF/M/RF/MPlasma type Primary Power during coating 100-500 W Frequency 13.56 MHzFrequency mode cw Temperature RF electrode 30-35° C. Monomer1H,1H,2H,2H-Perfluorooctyl acrylate Flow 40-100 sccm Pressure Basepressure 10-50 mTorr Work pressure 20-80 mTorr Residence time in plasma3 minutes zone during coating Oleophobicity Level 5 (ISO 14419-2010)

The coated textiles have been washed according to ISO 15797 (2002).

One complete washing cycle comprised the following steps:

-   -   1. Washing at 75° C. and using 20 g IPSO HF 234 without optical        whitener per kilogram dry textile material;    -   2. Drying in a drying cabinet;

After one washing cycle the oil repellency was measured according to ISO14419 and a spray test was performed according to ISO 9073—part 17 andISO 4920.

Next, four more washing cycles have been completed and the oilrepellency test and spray test have been repeated (values measured after5 washings).

Next, five more washing cycles have been done and the oil repellencytest and spray test have been repeated (values measured after 10washings).

The oil repellency as a function of the number of washing cycles ispresented in FIG. 12. FIG. 13 shows the spray test results in functionof the number of washing cycles.

From tables 13 and 14 it is clear that the textile samples that werepre-treated prior to coating have a better performance in washing. Theimprovement is more pronounced in spray testing, where the waterrepellency is tested. The difference in the level of oil repellencybecomes visible after 10 washing cycles, as can be seen in FIG. 12.After 20 washing cycles the pre-treated fabric still has oil repellencylevel 3.

Abrasion Durability

Three different polyester woven fabrics coated with a low power plasmacoating according to Example 2 have undergone an Martindale abrasiontest. Because afterwards a spray test was performed, larger samples thannormal were needed, and the set-up was slightly changed.

A standard wool fabric was pressed with a force of 9 kPa onto a largercoated PES woven fabric. 5000 abrasion cycles have been done and the oilrepellency was measured according to ISO 14419 and a spray test wasperformed according to ISO 9073—part 17 and ISO 4920. Then 5000 moreabrasion cycles have been done and the oil repellency test and spraytest have been repeated.

FIG. 14 shows the oil repellency in function of the number of Martindaleabrasion cycles and FIG. 15 shows the spray test results in function ofthe number of Martindale abrasion cycles.

The invention claimed is:
 1. A method of coating a fabric with a polymercoating, which method includes contacting a fabric with a monomer andsubjecting the monomer to plasma polymerisation, wherein the monomercomprises the general formula (I):C_(n)F_(2n+1)C_(m)X_(2m)CR₁Y—OCO—C(R₂)═CH₂ wherein n is 2 to 6, m is 0to 9, X and Y are H, F, Cl, Br or I, R₁ is H or alkyl or a substitutedalkyl and R₂ is H or alkyl or a substituted alkyl, wherein the methodcomprises a step of outgassing the fabric in a plasma chamber beforedeposition of the coating in which the outgassing is performed bypumping away moisture and trapped gases from the fabric and away fromthe plasma chamber, whilst winding the fabric from a first roller to asecond roller, and wherein the fabric is guided between said rollersduring the step of subjecting the monomer to plasma polymerization inthe plasma chamber.
 2. A method according to claim 1, wherein after theoutgassing step, the pressure inside the chamber is below a set basepressure for a next step which is a pre-treatment step or the plasmapolymerisation step.
 3. A method according to claim 1, wherein duringthe step in which the outgassing is performed by pumping away moistureand trapped gases whilst winding the fabric from a first roller to asecond roller, the fabric passes through a zone for a plasma without aplasma being present.
 4. A method according to claim 3, wherein thefabric is wound forwards and backwards between the first and secondrollers at least two times for outgassing of the fabric, the fabricpassing through a zone for a plasma without the plasma being present. 5.A method according to claim 3, wherein the outgassing is performed withthe fabric passing the plasma zone at a speed from 1 to 20 m/min.
 6. Amethod according to claim 1, wherein the polymer coating has a thicknessof from 30 to 100 nm.
 7. A method according to claim 1, the methodfurther comprising the step of coating one or both surfaces of thefabric.
 8. A method according to claim 1, further comprisingpre-treating a roll of fabric prior to coating deposition, including thesteps of winding the fabric between rollers, passing the fabric througha plasma zone, introducing an inert gas or a reactive and/or etching gasinto the plasma zone, causing a plasma to form in the plasma zone.
 9. Amethod according to claim 8, wherein the pre-treatment is performed withthe fabric passing the plasma zone at a speed from 1 to 20 m/min.
 10. Amethod according to claim 8, wherein the outgassing and thepre-treatment are combined in one single process step.
 11. A methodaccording to claim 8, wherein power for pre-treatment is applied eitherin continuous wave mode or pulsed mode, wherein when the power isapplied in pulsed mode, the pulse frequency is from 100 Hz to 10 kHz andthe duty cycle is from 0.05% to 50%.
 12. A method according to claim 1,wherein power for plasma polymerisation is applied either in continuouswave mode or pulsed mode, wherein when the power is applied in pulsedmode, the pulse frequency is from 100 Hz to 10 kHz and the duty cycle isfrom 0.05% to 50%.
 13. A method according to claim 1, further comprisingthe step of utilising the monomer to strike plasma without using anadditional gas to strike the plasma.
 14. A method according to claim 1,wherein the fabric comprises a synthetic material.
 15. A methodaccording to claim 1, wherein R₁ is an at least partiallyhalo-substituted alkyl.
 16. A method according to claim 1, wherein R₂ isan at least partially halo-substituted alkyl.
 17. A method according toclaim 1, wherein the fabric comprises natural fibres.